The answer is that you must update the KMS key policy to grant the partner account the `kms:Decrypt` permission. This is required because when an S3 bucket is encrypted with SSE-KMS using a customer-managed key, the bucket policy controls access to the S3 API actions like `s3:GetObject`, but it cannot authorize the use of the KMS key itself. The KMS key policy acts as a separate, independent layer of access control; without explicitly allowing the partner account to call `kms:Decrypt`, the object remains encrypted and unreadable even if the bucket policy permits the read. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of the shared responsibility model for encryption—specifically that KMS policies are resource-based and must be explicitly configured for cross-account access. A common trap is assuming the bucket policy alone is sufficient or that the partner needs access to the bucket’s encryption configuration. Remember the memory tip: "Bucket for read, KMS for decrypt—both policies must connect."
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A data engineer is configuring an S3 bucket policy to allow cross-account access for a partner account to read objects. The bucket is encrypted with SSE-KMS using a customer-managed key. What additional configuration is needed to allow the partner account to decrypt the objects?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Update the KMS key policy to grant the partner account kms:Decrypt permission
For cross-account access with SSE-KMS, the KMS key policy must grant the partner account access to use the key. The bucket policy alone is insufficient. The partner account does not need VPC endpoints, and the bucket policy for decryption is not needed. The partner account does not need access to the S3 bucket's encryption configuration.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Add a bucket policy that grants the partner account s3:GetObject
Why it's wrong here
This allows read access to the S3 object, but without KMS key permissions, the partner cannot decrypt.
✗
Create a VPC endpoint for S3 and add it to the bucket policy
Why it's wrong here
VPC endpoints are for private connectivity, not for granting decryption permissions.
✓
Update the KMS key policy to grant the partner account kms:Decrypt permission
Why this is correct
The KMS key policy must allow the partner account to use the key for decryption.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a bucket policy that grants s3:GetObject and s3:GetEncryptionConfiguration
Why it's wrong here
The encryption configuration is not needed for decryption; the KMS key permission is required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Data Security and Governance — This question tests Data Security and Governance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Update the KMS key policy to grant the partner account kms:Decrypt permission — For cross-account access with SSE-KMS, the KMS key policy must grant the partner account access to use the key. The bucket policy alone is insufficient. The partner account does not need VPC endpoints, and the bucket policy for decryption is not needed. The partner account does not need access to the S3 bucket's encryption configuration.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A data engineer needs to share an S3 bucket with another AWS account. They want to ensure that the objects in the bucket remain encrypted with SSE-KMS using a customer managed key. What additional step is required for cross-account access?
medium
✓ A.Modify the KMS key policy to grant the target account kms:Decrypt permission
B.Add an IAM policy in the target account to allow kms:Decrypt
C.Disable SSE-KMS encryption on the bucket
D.Add a bucket policy that grants the target account s3:GetObject
Why A: When using SSE-KMS with a customer managed key, the key policy must grant the target account's IAM role or user permission to use the key. S3 bucket policy and IAM permissions are also required, but the key policy is the additional step specific to KMS. Option A is wrong because the bucket policy alone does not grant KMS permissions. Option B is wrong because the target account's IAM policy alone cannot override the key policy. Option D is wrong because disabling encryption is not required.
Last reviewed: Jun 20, 2026
Question Discussion
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This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.
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